The concept of gas valves is well known in the art, typically these gas valves have an inlet and an outlet with a diaphragm chamber that is vented to the atmosphere to allow the diaphragm to move within the gas valve. The flow of gas though the gas valve is controlled by the diaphragm within the gas valve. In winter climates, the gas vent can become clogged with snow or ice which prevents the gas valve from operating properly. The present invention comprises a one-piece weather cap that can be installed on an existing valve without the use of tools to prevent the gas vent from becoming clogged with snow, ice, or other forms of moisture. The one-piece weather cap allows the gas vent to breathe and is held on to the gas valve through a frictional and flexible neck that engages a portion of the valve, while the other portions of the valve including the gas vent are shielded by a skirt that is cantilevered radially outward from the neck of the weather cap. A further feature of the invention is that one can make adjustments to the valve simply by slipping the weather cap off the valve to thereby expose the valve.